1. Field of the Invention
This invention relates to meta-aramid articles, e.g., fibers, fabrics and the like. In one aspect the invention relates to dyeing meta-aramid articles while in another aspect the invention relates to facilitating the dyeing of meta-aramid articles through the use of benzoate carrier.
2. Description of the Related Art
Meta-aramid articles, e.g., fibers such as NOMEX™ and CONEX™ (both polymetaphenylene isophthalic amide, which is formed by the reaction of meta-phenylenediamine and isophthaloyl chloride, and produced by DuPont and Teijin respectively), are used in various applications, largely for their fire resistant properties. Due to their hydrophobic nature, these articles are difficult to dye in typical aqueous dye baths as the dye molecules cannot easily penetrate the article.
In order to facilitate dye penetration, a carrier (sometimes referred to as a dye assist or solvent) must be used to swell the article and facilitate dye transport. The first commonly used carrier was acetophenone but it has fallen from favor due to odor and toxicity issues, and other carriers have been introduced or suggested as alternatives. For example, US 2005/0014435A1 describes the dyeing of aramid fibers with a dye bath formulated with CYNDAE C-45 (available from Bozzetto, Inc.) as a dye assist. JP 60162883 describes the use of a glycol ether (triethylene glycol monophenyl ether) in a dye bath for polyamide fibers. WO2006/122887A2 describes the use of another glycol ether (1-phenoxy-2-propanol) in the preparation of dye baths. US2002/0144362A1 describes 3,5,5-trimethyl-2-cyclohexen-1-one, also known as isophorone, as a dye carrier for polyamide fibers. This patent also references alkyl ketones and N-alkyl phthalimides as dye carriers. U.S. Pat. No. 6,132,476 describes the use of benzyl alcohol, N-alkyl pyrrolidones, N,N-dialkyl-benzamides, and aryl ether as dye carriers. U.S. Pat. No. 6,840,967 describes the use of ethylene glycol phenyl ether, and various amides and amines as dye carriers. JP 08134370 A2 describes the use of several glycol ethers, namely diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and diethylene glycol monobenzyl ether as dye carriers. Butyl benzoate is mentioned as a dye carrier by T. Vigo in “Textiles Processing and Properties—Preparation, Dyeing, Finishing, and Performance”, Textile Science and technology 11, Elsevier Publishing, 1994, p 137.
Despite the identification and proposed uses of these many and varied dye carriers, interest remains in identifying new dye carriers for use with meta-aramid articles, particularly fibers, that are performance competitive with acetophenone but without the odor and toxicity issues associated with the use of acetophenone.